Cranial Cruciate Ligament Rupture & Repair

Cranial Cruciate Ligament Rupture • Diagnosis • Treatment

Cranial cruciate ligament rupture is the most common orthopedic injury in the dog. The ligament can rupture due to trauma or more commonly due to premature degeneration of its structure. The cranial and caudal cruciate ligaments together with other structures surrounding the knee (medial and lateral meniscus, collateral ligaments and joint capsule) help to stabilize and support the joint through its full range of motion. The cranial cruciate ligament is one of the major stabilizers of the knee running from the front of the knee to the back. More specifically the cranial cruciate ligament keeps the tibia from sliding cranially (forward) beneath the femur when the limb bears weight. It also limits medial (internal) rotation of the tibia when the knee is flexed. If the cranial cruciate ligament is ruptured the tibia slides cranially (forward) with each step causing pain and inflammation. Over time the meniscal cartilages, which also provide stability and act as shock absorber, become crushed and torn. Lameness, muscle atrophy, arthritis and pain will result.

Diagnosis of Cranial Cruciate Rupture:
A diagnosis of a cranial cruciate ligament rupture can be made by testing the stability of the knee. If it is a complete tear the veterinarian will diagnose instability by performing a “tibial thrust” test and a “cranial drawer” test. Partial tears may be more difficult to diagnose so other physical finding, such as muscle atrophy and joint swelling may help support the diagnosis when only minimal changes in stability are noted. Although a torn ligament will not be seen with radiographs they often aid in the diagnosis and will note the amount of arthritis in the knee.

Treatment Options for Cranial Cruciate Ligament Rupture:
There is no cure for a torn cranial cruciate ligament. The goals for all treatments are to relieve pain and improve function.Nonsurgical Treatment:
Nonsurgical treatment entails rest and pain management for 6 to 8 weeks. After this period exercises to improve strength and range of motion should be initiated. If necessary a weight loss program should begin. However, the success rate for accomplishing our goals is not high and typically only small dogs may have good long-term result with this approach.Surgical Treatment for Cranial Cruciate Rupture:
The surgical options are numerous however, no procedure attempts to repair the ruptured ligament. The most common procedures used today by surgeons can be divided into two broad categories, osteotomies and extracapsular lateral sutures. Osteotomies are bone cutting procedures that change the biomechanics (anatomy) of the knee. Extracapsular techniques are procedures that attempt to replace the function of the cranial cruciate ligament outside the joint capsule.

Tibial Plateau Leveling Osteotomy (TPLO)
Tibial Plateau Leveling Osteotomy is a bone cutting surgery. TPLO surgery stabilizes the knee by changing the biomechanical forces in the joint. The tibial plateau is the articular surface on top of the tibia. It is not flat but sloped with an angle (Tibial Plateau Angle), each specific to the dog around 20 to 30 degrees. With the cranial cruciate ligament in place the articular surface of the femur is in contact with the tibial plateau and the weight of the dog is transferred across the joint. Without the ligament (i.e. torn ligament) the femur slides down the angled tibial plateau pushing the tibia cranially (forward). If the slope or Tibial Plateau Angle could be reduced or Level, the ligament would no longer be needed and the tibia would no longer slide forward causing pain, inflammation and minimize injury to the meniscal cartilage. In order to Level the Tibial Plateau a semicircular cut or Osteotomy is made in the bone. This portion of the bone is then rotated to achieve a 5 degree angle. The bone is then stabilized with a bone plate and screws. A TPLO can be offered to most sizes of dogs and most surgeons recommend a TPLO or other biomechanical altering surgical technique for large dogs, athletic dogs or dogs with disease in the other knee. At this time, the TPLO is considered the gold standard for treatment of cranial cruciate ligament disease. All other techniques are compared to the outcome of the TPLO surgery.

Tibial Tuberosity Advancement (TTA)
Tibial Tuberosity Advancement is another bone cutting surgery. TTA surgery also stabilizes the knee by changing the biomechanical forces in the knee. The forces are rebalanced to limit the tibia from slipping forward. In this procedure, the bony attachment of the quadriceps muscles is cut, moved forward, and held in place with a spacer, plate and screws while healing.

Extracapsular Lateral Suture
Extracapsular Lateral Suture is not a bone cutting procedure and does not alter the anatomy of the knee. Instead, it is a surgical procedure in which nylon or some form of suture is placed outside the joint capsule. The suture is secured to the bone providing temporary stability to the knee as the dog makes new scar tissue around the knee for long term stability. TightRope CCL- is a form or Extracapsular Lateral Suture repair in which a special suture called FiberTape is used. This is a Kevlar-like material that is used extensively in human surgery for many orthopedic applications. This material has properties that make it stronger and less prone to failure than any other suture materials currently being used for cranial cruciate lateral suture repair. Extracapsular Lateral Suture has limitations and may fail in larger or athletic dogs or dogs with disease in their other knee.